Vacuum evaporation apparatus



March 13, 1962 B. l. BERTELSEN VACUUM EVAPORATION APPARATUS Filed July1, 1958 RE COIL 6 RF. GENERATOR & CONTROL MEANS COOLANT PUMP VACUUM PUMPT ICE-J.

13 REFRACTORY BASE INVENTOR BRUCE I. BERTELSEN F IG 3 AGENT UnitedStates Patent Ofiice 3,024,761 Patented Mar. 13, 1962 3,024,761 VACUUMEVAPORATION APPARATUS Bruce I. Bertelsen, Vestal, N.Y., assignor toInternational Business Machines Corporation, New York, N.Y., acorporation of New York Filed July 1, 1958, Ser. No. 745,988 7 Claims.(Cl. 118-49.1)

The invention relates to apparatus for coating various substrates byvacuum evaporation and deposition.

An object of the invention is to provide an improved process andsimplified apparatus for obtaining thin films upon a substrate.

Another object is to provide a process and an apparatus whereby the rateof evaporation may be easily controlled to provide deposited films ofdefinite and uniform thick ness.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of examples, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

FIG. 1 is the preferred embodiment showing a base cylinder constitutedof the material to be evaporated secured to an R-F coil, all enclosedwithin a vacuum chamber.

FIGS. 2 and 3 show how the refractory base cylinder is subjected,respectively, to spraying and electroplating processes for applying thematerial on the cylinder, which material is to be evaporated.

The preferred form of the apparatus constituting the invention is seenin FIG. 1. This apparatus is contained within an evacuable chamber 1formed by means consisting of a bell dome 2. The latter is movable intoand out of sealing engagement with a base plate 3. The chamber 1communicates with vacuum pump means 4 through a conduit 5. The pumpmeans 4 may be any suitable pump means well known in the art. The sourcefor evaporating coating material in the chamber 1 comprises an inductionR-F coil 6 communicating with a coolant pump 7 by means of conduits 8and 9. The coolant used depends upon the temperature requirement of theR-F coil-for elevated temperatures, liquid sodium or silicones may beused; for lesser temperatures, oil may be used; and, for lowertemperatures, water is used. The coil 6 is further connected to an R-Fgenerator and control means 10 by means of leads 11 and 12, the R-Fgenerator 1t) supplying high-frequency current suitable for apparatus ofthis type. This means 10 further contains regulating control means forcontrolling the rate of frequency of the current. The coil 6 furthersupports a sheet 13 of the material which is to be evaporated. The sheet13 may be configured in the same manner as the supporting R-F coil 6. Inthe preferred embodiment shown, the coil and sheet material arecylindrical in shape; this arrangement providing optimum conditions ofcontrol. However, at the expense of optimum conditions, the shape maytake forms other than cylindrical; for example, rectangular, elliptical,etc. Thus, the current carrier means for supplying heat to the sheet, orbase, may have configurations other than circular.

The sheet 13 is secured to the coil 6 by welding, solder ing, brazing,or by any other suitable process whereby intimate electrical contact isachieved. In operation, the high-frequency current applied to the coil 6is thereby applied to the sheet 13 and causes maximum concentratedheating to occur on a peripheral band edge 13a (molten zone) of thesheet 13. This is developed by virtue of the skin effect and the coolingat the bottom edge of the sheet 13. By virtue of this arrangement, theamount of metal to be evaporated and the rate of evaporation can beaccurately controlled. This by regulating the degree of coolness of thecoil and the frequency of the RF generator. The cooling of the coil is,of course, determined by the nature and temperature of the coolantcirculating through the coil 6, the coolant pump 7 temperatureregulating, not shown, well known in the art. The temperature of theperipheral band edge 13a of the sheet 13 can be accurately determined byknowing the depth, or length, and thickness of the sheet 13. Heattransfer to the coil is thus predetermined on the basis of theseparameters. Higher temperatures narrow the hot band, this beingcontrolled by increasing the frequency of the R-F current applied.

Another embodiment is shown in FIG. 2. Here the base referenced as 13'is comprised of a refractory base material upon which the metal to beevaporated is applied by any suitable application process; for example,spraying. As seen in FIG. 2, the base 13 is coated by a conventionalspraying apparatus of which spraying nozzle 15 forms a part thereof. Thesprayed base is then secured to the R-F coil 6 in the manner explained.Another method by which the metal to be evaporated may be applied is bymeans of a brush.

In FIG. 3, there is shown schematically how the refractory base 13 maybe coated with the metal to be evaporated by an electroplating process.In this process, the base 13 is partially immersed in an electrolyte 30contained in a plating tank 31 to which an electrical current suitablefor electroplating is applied from a source 32 to pass through theelectrolyte and base 13'; the electrolyte containing the metal insolution. The depth to which the base 13 is immersed is dependent uponthe amount or" metal to be plated to the base. Other forms of chemicaldeposition may be employed for applying the material to the refractorybase 13.

The refractory base 13 may be constituted of metals capable ofwithstanding elevated temperatures and which are electrically conductiveand are not affected by the evaporation process; such metals being, forexample, tung sten, tantalum, molybdenum, hafnium, niobium, rhenium, andplatinum.

The metals that may be applied to the refractory base may be any metalwhich is capable of being vaporized; for example, iron, cobalt, nickel,the noble metals, alloys, and others.

Any suitable means for supporting the substrate above and near theevaporating source material may be employed; as seen in FIG. 1, asupport is used which comprises a base 20 having an unadjustable shaft21 and an adjustable platform 22 for supporting the substrate in anyposition with respect to the peripheral edge 13a of the base 13.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in theart, without departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. In apparatus for providing thin films upon a substrate by evaporationand deposition in a vacuum, the combination comprising a single openloop configured electrical current carrier contained in the vacuum; asource of R-F current including means for supplying R-F current to saidcarrier to cause the latter to eflfect evaporation; and a slotted curvedsheet of evaporable material, having substantially the sameconfiguration as the carrier, the open loop of said carrier and the slotof said sheet being in substantial alignment to prevent electricalshort- 3 ing, said sheet supported by and having electrical contact withsaid carrier whereby the more remote edge of said sheet is subjected tomaximum heating to cause evaporation along the remote edge of said sheetupon the flow of R-F current through said sheet.

2. Apparatus, as in claim 1, in which means are provided to circulate acoolant through said R-F current carrier.

3. Apparatus, as in claim 1, in which said current carrier has acircular configuration, and the sheet supported thereby havingsubstantially a cylindrical configuration.

4. In apparatus for providing thin films on substrates by evaporationand deposition in a vacuum, the combination comprising a single openloop configured electrical current carrier contained in the vacuum, asource of R-F current including means for applying R-F current to saidcarrier, a slotted figured sheet of refractory evaporable metal bearinga layer of metal, and means for securing said sheet to establishelectrical contact with said layer whereby the remote band edge of saidsheet is subjected to maximum heating to cause vaporization of saidlayer upon the application of the RF current, the open loop of saidcarrier and the slot of said sheet being aligned to prevent electricalshorting.

5. Apparatus, as in claim 4, further having means for supporting thesubstrates in proximity to the remote edge of said sheet.

6. Apparatus, as in claim 4, in which said current carrier comprises ahollow coil and said sheet being substantially similarly configuredalong its cross section.

7. Apparatus, as in claim 6, further including means for circulating acoolant through said coil.

References Cited in the file of this patent UNITED STATES PATENTS2,267,343 Scott et al Dec. 23, 1941 2,378,476 Guellich June 19, 19452,459,971 Stanton Jan. 25, 1949 2,584,660 Bancroft Feb. 5, 19522,671,034 Steinfeld Mar. 2, 1954 2,778,485 Gabbrielli Jan. 22, 19572,802,187 Evans et al Aug. 6, 1957 2,909,585 Tudbury Oct. 20, 1959FORElGN PATENTS 599,372 Great Britain Mar. 11, 1948 701,790 GreatBritain Jan. 6, 1954

